【作者】 周代伟；

【导师】 杜朝辉； 阳虹；

【作者基本信息】 上海交通大学 ， 动力工程， 2008， 硕士

【摘要】 汽轮机叶片是汽轮机的关键零件,对于汽轮机的安全运行至关重要。叶片可能在因气流的周期性扰动力作用下发生异常振动,从而导致高周或低周疲劳失效。利用叶冠之间的干摩擦力产生的阻尼,是一种有效抑制叶片振动、降低叶片动应力的有效手段。因此研究叶冠干摩擦阻尼的减振机理十分必要。本文围绕汽轮机中带阻尼减振装置(此处指叶冠)叶片的固有振动特性及动力响应特性,开展了以下工作:(1)用有限元法计算了平行冠叶片的固有振动特性。计算了某汽轮机中压第一级和第十三级动叶片在不同载荷条件下的固有频率。在工作载荷下,这两种叶片的周向一弯固有频率分别为:1027.2Hz和199.66Hz,计算结果同实验结果非常接近。(2)计算了锯齿冠叶片的固有振动特性。利用ANSYS软件非线性接触的功能,计算了锯齿冠在不同转速下的接触应力和接触区域的变化。计算结果表明:在零转速和100%工作转速下的周向一弯固有频率分别为100.9Hz和139.7Hz,在35%工作转速附近叶冠之间开始发生接触,叶片可能在此转速以后呈现整圈振动特性。(3)建立了带冠叶片的干摩擦阻尼模型,将叶冠接触面之间的干摩擦力变换为等效刚度和等效阻尼。根据该模型进行了算例验证,本文计算结果同相关文献的计算结果对比表明:本文建立的干摩擦阻尼模型和计算方法是正确有效的。(4)计算了平行冠和锯齿冠叶片的谐响应特性。编制fortran程序和命令流文件,可用于自动构造接触区域的阻尼矩阵和刚度矩阵,并计算了考虑干摩擦阻尼作用下叶片动应力,与未考虑干摩擦阻尼的计算结果相比,动应力下降了约50%。更多还原

【Abstract】 Turbine blade is the key component of the steam turbine. It is very important to the safety of the steam turbine. Turbine blade will vibrate under the periodic exciting force of the steam, which will lead to the high frequency and low frequency fatigue failure. The dry friction damp between the shroud of the blades could restrain the vibration of the blades and reduce the dynamic stress of the blade, so it is necessary to research the principle of the dry friction damper. The main contents are as following:(1) Finite element method is used to study the modal of the turbine blade with parallelogram shroud. Under the working conditions, the first natural frequency of the 1st and 13th stage turbine are 1027.2Hz and 199.66Hz respectively, which meets the experiment result very well.(2) Finite element method is also used to study the modal of the turbine blade with zigzag shroud. The contact stress and the variation of contact zone between the zigzag shroud is studied by using the contact analysis function of the ANSYS software. The result shows that the first natural frequency of this blade is 100.9Hz and 139.7Hz under zero and 100% working rotation speed respectively. The shroud begins to contact at the rotation speed about 35% working rotation speed.(3) Mathematic model of the dry friction damper between shroud is built to transfer the dry friction force to equivalent stiffness and damp. A test case is calculated by using this model, and the result meets good with that of some reference, which shows the validity of this model. (4) Harmonic response of the two types blade are carried out. Fortran language and ANSYS parametric design language are used to develop a program which could construction the damp matrix and stiffness matrix automatically and then calculate the dynamic stress of the blade under periodic exciting force. The result shows that the dynamic stress value reduces about 50% compared to that without dry friction damp.更多还原